1. Field of the Disclosure
The disclosure relates generally to the field of networking and content delivery. In one exemplary aspect, the disclosure relates to the use of a network architecture for providing packetized content as a multicast and as a unicast via a content distribution (e.g., cable, satellite) or other network.
2. Description of Related Technology
The provision of content to a plurality of subscribers in a network is well known. In a typical configuration, the content is distributed to the subscribers' devices over any number of different topologies including for example: (i) Hybrid Fiber Coaxial (HFC) network, which may include e.g., dense wave division multiplexed (DWDM) optical portions, coaxial cable portions, and other types of bearer media; (ii) satellite network (e.g., from an orbital entity to a user's STB via a satellite dish); (iii) optical fiber distribution networks such as e.g., “Fiber to the X” or FTTx (which may include for example FTTH, FTTC, FTTN, and FTTB variants thereof); (iv) Hybrid Fiber/copper or “HFCu” networks (e.g., a fiber-optic distribution network, with node or last-mile delivery being over installed POTS/PSTN phone wiring or CAT-5 cabling); (v) microwave/millimeter wave systems; etc.
Various types of content delivery services are utilized in providing content to subscribers. For example, certain content may be provided according to a broadcast schedule (aka “linear” content). Content may also be provided on-demand (such as via video on-demand or VOD, free video on-demand, near video on-demand, etc.). Content may also be provided to users from a recording device located at a user premises (such as via a DVR) or elsewhere (such as via a personal video recorder or network personal video recorder disposed at a network location) or via a “startover” paradigm, which also affords the user increased control over the playback of the content (“non-linear”).
Just as different varieties of content delivery services have evolved over time, several different network architectures have also evolved for deploying these services. These architectures range from fully centralized (e.g., using one or more centralized servers to provide content to all consumers) to fully distributed (e.g., multiple copies of content distributed on servers very close to the customer premises, at the “edge” of the distribution network), as well as various other configurations. Some distribution architectures (e.g., HFC cable, HFCu, etc.) consist of optical fiber towards the “core” of the network, which is in data communication with a different medium (coaxial cable radio frequency, copper POTS/PSTN wiring, etc.) distribution networks towards the edge.
While the details of how video is transported in the network can be different for each architecture, many architectures will have a transition point where the video signals are modulated, upconverted to the appropriate channel (e.g., RF channel), and sent over the coaxial segment(s), copper wiring, (or air interface) of the network. For example, content (e.g., audio, video, etc.) is provided via a plurality of downstream (“in-band”) RF QAM channels over a cable or satellite network. Depending on the topology of the individual plant, the modulation and upconversion may be performed at a node, hub or a headend. In many optical networks, nodes receive optical signals which are then converted to the electrical domain via an optical networking unit (ONU) for compatibility with the end-user's telephony, networking, and other “electrical” systems.
In U.S. cable systems for example, downstream RF channels used for transmission of television programs are 6 MHz wide, and occupy a 6 MHz spectral slot between 54 MHz and 860 MHz. Within a given cable plant, all homes that are electrically connected to the same cable feed running through a neighborhood will receive the same downstream signal. For the purpose of managing services, these homes are aggregated into logical groups typically called service groups. Homes belonging to the same service group receive their services on the same set of in-band RF channels.
Broadband data carriage in such networks is often accomplished using other (typically dedicated) QAM channels. For instance, the well known DOCSIS specifications provide for high-speed data transport over such RF channels in parallel with the video content transmission on other QAMs carried on the same RF medium (i.e., coaxial cable). A cable modem is used to interface with a network counterpart (such as a content delivery network (CDN) device) so as to permit two-way broadband data service between the network and users within a given service group.
Out-of-band (OOB) channels (and associated protocols) may be used to deliver metadata files to a subscriber device, as well as to provide communication between the headend of the content-based network and the subscriber devices.
Other systems and methods may also be used for delivering media content to a plurality of subscribers. For example, so-called “Internet Protocol Television” or “IPTV” is a system through which services are delivered to subscribers using the architecture and networking methods of an Internet Protocol Suite over a packet-switched network infrastructure (such as e.g., the Internet and broadband Internet access networks), instead of being delivered through traditional radio frequency broadcast, satellite signal, or cable television (CATV) formats. These services may include, for example, Live TV, Video On-Demand (VOD), and Interactive TV (iTV). IPTV delivers services (including video, audio, text, graphics, data, and control signals) across an access agnostic, packet switched network that employs the Internet Protocol (IP). IPTV is managed in a way so as to provide the required level of quality of service (QoS), quality of experience (QoE), security, interactivity, and reliability via intelligent terminals such as PCs, STBs, handhelds, TV, and other terminals. IPTV service is usually delivered over a complex and heavy “walled garden” network, which is carefully engineered to ensure sufficient bandwidth for delivery of vast amounts of multicast video traffic.
IPTV uses standard networking protocols for the delivery of content. This is accomplished by using consumer devices having broadband Internet connections for video streaming. Home networks based on standards such as “next generation” home network technology can be used to deliver IPTV content to subscriber devices in a home.
So-called “Internet TV”, on the other hand, generally refers to transport streams sent over IP networks (normally the Internet) from outside the network (e.g., cable, HFCu, satellite, etc.) that connects to the user's premises. An Internet TV provider has no control over the final delivery, and so broadcasts on a “best effort” basis, notably without QoS requirements.
There are also efforts to standardize the use of the 3GPP IP Multimedia System (IMS) as an architecture for supporting IPTV services in carrier's networks, in order to provide both voice and IPTV services over the same core infrastructure. IMS-based IPTV may be adapted to be compliant with the IPTV solutions specifications issued by many IPTV standards development organizations (SDOs), such as, e.g., Open IPTV Forum, ETSI-TISPAN, ITU-T, etc.
While delivery of packetized (e.g., IP) content is well known in the prior art, the ability to provide delivery of packetized media content to a subscriber device over a content delivery network (e.g., cable television RFC, HFCu, satellite, etc.), other than over the Internet as afforded by virtue of a satellite, cable, or other such modem (i.e., “Internet TV”), and/or by using extant spectrum resources (e.g., via a CDN), has been lacking.
Particular systems have been developed to provide either unicast or multicast delivery of IP content. However, the foregoing systems may utilize adaptive bitrate (ABR) streams that are provided to requesting devices via unicast mechanisms (i.e., each user streams an individual copy of the requested content). Therefore, delivery of the packetized media content in a content delivery network as discussed above would be greatly bandwidth-inefficient. That is to say, typical content delivery networks do not have sufficient bandwidth capacity to support unicast delivery of IP packetized content to a large number of users or subscribers. Moreover, most network topologies and architectures (such as those discussed above) have a more efficient “multicast” capability which more effectively uses available bandwidth; however, most IP-enabled client devices do not support such multicast, and hence networks are relegated to use of the less efficient unicast or similar mechanism for delivery of IP streams.
As noted previously, today's IP video delivery from video server to video client has mainly two approaches: (i) IP multicast; and (ii) IP unicast. In IP multicast environment, one multicast video stream can be shared and viewed by many video clients. In IP unicast environment, each of the video client has its own video stream, although some of the viewers may view the same contents. A typical IP multicast can have significant bandwidth saving advantages when many viewers are viewing same programs. On the other hand, using the ABR (adaptive bit rate) technology, IP unicast allows video client to switch to video stream of different quality/bitrate in the different network environment to improve a viewer's viewing experience. For example, an IP unicast video client can request a video stream that has lower bitrate when low network bandwidth is available, and request a video with higher quality/bitrate when more bandwidth is available. In other words, IP unicast is more effective at managing changes in the network bandwidth, CPU, etc. as compared to an IP multicast delivery. Additional advantages of an IP unicast delivery include guaranteed packet delivery in a lossy network (at the cost of packet re-transmission through the entire network). However, overall the IP unicast delivery mode is significantly more taxing on the available bandwidth in a network, which is particularly salient when the network topology and infrastructure are constrained with a fixed bandwidth, or limited “build-out” capacity.
Hence, it would be desirable to provide mechanisms to take advantage of the benefits of an IP multicast and an IP unicast by combining these (i.e., in a cooperative or hybrid approach). Ideally, in one implementation, such mechanisms would achieve the network bandwidth saving benefit of IP multicast, and at the same time to preserve the viewer's viewing experience of IP unicast. Additionally, such mechanisms would enable a network operator to facilitate broadcast viewership for live television via IP streaming.